Problem: If $x \veebar y = x+7y$ and $x \bigtriangledown y = x^{2}+4y^{2}$, find $-2 \bigtriangledown (5 \veebar -1)$.
Explanation: First, find $5 \veebar -1$ $ 5 \veebar -1 = 5+(7)(-1)$ $ \hphantom{5 \veebar -1} = -2$ Now, find $-2 \bigtriangledown -2$ $ -2 \bigtriangledown -2 = (-2)^{2}+4(-2)^{2}$ $ \hphantom{-2 \bigtriangledown -2} = 20$.